Workshop Technology
In a four high rolling mill, there are four rolls out of which

Two are working rolls and two are backing up rolls
One is working roll and three are backing up rolls
Three are working rolls and one is backing up roll
All of the four are working rolls

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Workshop Technology
During hot working of metals

Grain structure of the metal is refined
Porosity of the metal is largely eliminated
Mechanical properties are improved due to refinement of grains
All of the listed here

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